All technologies provide less light output over time, but light-emitting diodes (LED) depreciate much more slowly compared to incumbent technologies.

And unlike previous technologies, LED vendors have a greater impact on the rate of lumen depreciation based on luminaire design. So in addition to an application-based lighting design, a cost/benefit analysis should always include an appropriate lumen maintenance factor that helps predict depreciation.

BetaLED's “Recommended Lumen Maintenance Factors (TD-13)” guides customers through the process of determining what lumen maintenance value to use based on desired hours of operation (application life), ambient temperature, drive current, and region of the country. Based on data from the company's LED supplier, Cree Inc. of Durham, N.C., and available for free at www.betaled.com, the six-page document presents information a manufacturer should be able to provide to help you decide on the best configuration for a particular application.

Distributor Best LED Group in Hauppauge, N.Y., developed the chart above comparing BetaLED's LEDway luminaires to the existing system in Smithtown, N.Y.

Figures don't include maintenance-related savings, which the company estimated at $75,000 annually for every 1,000 streetlights converted to LED.

The LED luminaire has a projected service life of at least 15 years with no maintenance. HPS maintenance costs include lens cleaning, buying and stocking ballasts for different voltages and types, hazardous waste stream costs related to the mercury content of HPS bulbs, and replacing HPS bulbs every 20,000 hours.

ANNUAL SAVINGS: $75,000 on maintenance, $150,000 on electricity

Every year, U.S. government agencies spend more than $10 billion on natural gas, electricity, and heating oil to provide services and meet constituent needs. If cities and counties treated energy as a single expense, it would be the largest line item in the budget after payroll. So as they look for ways to free up limited resources, infrastructure managers are increasingly focusing on their buildings and other assets.

Located on the North Shore of Long Island in New York, Smithtown is committed to improving its carbon footprint and its finances. The town of 118,000 residents was the second city nationwide to convert its fleet of diesel-powered refuse trucks to compressed natural gas. A 50,000 kilowatt-hour photovoltaic system provides 10% of the power for the Municipal Service Facility building, the town's largest electricity consumer. It's soliciting bids for wind power.

Streetlighting is another target for potential savings.

When introduced in the 1980s, high-pressure sodium (HPS) was much more cost-effective than mercury vapor and, like many communities, Smithtown eventually installed 100- , 150- , 250- , and 400-watt HPS fixtures on all street-lights despite the occasional complaint regarding the lights' yellowish cast.

Even so, streetlights still account for up to 40% of municipalities' electric bills, according to the U.S. Energy Department; and Smithtown was no different.

Initially, the Traffic Safety Department planned to retrofit 1,100 lights — approximately 10% of Smithtown's 11,600 total — with induction fixtures to compare electricity consumption to HPS. Though induction provides longer lamp life, optical control — i.e., light distribution — is as difficult as, if not more so, than HPS. Such systems produce less uniform distribution that includes excess pools of light, called “hot spots,” directly below the luminaire and spilling light off the intended target, which residents dislike.

Unlike HPS or induction, light-emitting diodes (LED) offer much better optical control. Overall illumination, including light uniformity and direction, is much better. In addition, LEDs don't contain mercury, making them environmentally beneficial. Traffic Safety and Lighting Director Mitch Crowley wanted to include LED in his comparison, but after a year-long search hadn't found one that satisfied his distribution or light requirements for a streetlight application.

About the same time the American Recovery and Reinvestment Act of 2009 provided $275 billion in Energy Efficiency and Conservation Block Grants for highway repairs, weatherization, and other “green” upgrades, he saw BetaLED's LEDway luminaire. He was so impressed he jettisoned induction entirely and decided to extend the pilot program to determine if the luminaire would meet Smithtown's requirements and his expectations.

“We extended the pilot program for a month to be able to test the LED luminaire,” Crowley says. “We were so impressed with the product that we made the decision to install LED streetlights instead of induction.”

Ultimately, the department retrofit 1,143 lights. Crowley estimates the retrofits will cut the town's electricity bill 52% through lower negotiated rates with Long Island Power Authority while providing 15 years of virtually maintenance-free service (see chart on previous page for details). Since then, Smithtown has installed 550 more LEDways and budgeted $200,000 to $350,000 annually to continue retrofitting the remaining streetlights over the next three years.

“We're thrilled to be the first town on Long Island to commit to LED street-lights, which help with our strategy for better energy efficiency and greenhouse gas reduction,” says Supervisor Pat Vecchio.

Crowley tells colleagues who ask that he “loves the design, optics, light quality and control, and distance the light covers between luminaires. The product has a failure rate of less than 1% and is made in the United States; delivery within a few weeks wasn't like some of the products made overseas where I've waited months.”